Field of the Invention
The present invention relates to a detection apparatus, a lithography apparatus, and a method of manufacturing an article.
Description of the Related Art
An imprint technique is a technique of forming a micropattern on a substrate by using a mold on which the pattern is formed. An example of the imprint technique is a photocuring method. In the imprint technique using this photocuring method, a resin (photocuring resin) as an imprint material is supplied to a shot region (imprint region) of a substrate. Then, the resin on the substrate is irradiated with light in a state in which a pattern of a mold is in contact with (imprinted on) the resin, thereby curing the resin. After that, the pattern of the resin is formed on the substrate by separating (releasing) the mold from the cured resin.
When bringing the mold into contact with the resin on the substrate, it is necessary to accurately align the substrate and mold. As a method to be used in an imprint apparatus, a so-called, die-by-die method is known in which a substrate and mold are aligned by detecting a mark (mold-side mark) formed on the mold and a mark (substrate-side mark) formed in each shot region of the substrate.
The imprint apparatus adopts TTM (Through The Mold) alignment which detects a substrate-side mark through a mold. Also, the TTM alignment uses a dark-field detection system which detects diffracted light generated by a mold-side mark and substrate-side mark (see Japanese Patent Laid-Open No. 2007-42965). The dark-field detection system is preferably arranged near a mold, but mechanical interference may occur between the dark-field detection system and the upper portion of the mold. When emitting light for curing a resin on a substrate, therefore, the dark-field detection system must be retracted from the vicinity (above the mold) of the mold. To avoid this mechanical interference, the use of an imaging optical system which projects an alignment mark is known. The use of the imaging optical system makes it unnecessary to retract the dark-field detection system when irradiating the resin on the substrate with light. This can increase the productivity of the imprint apparatus.
In the TTM alignment using the imaging optical system, however, the aberration of the imaging optical system causes an alignment error because the alignment mark projected by the imaging optical system is detected. The main cause of this alignment error is the asymmetry of an image such as a coma aberration. To decrease the alignment error, it is necessary to decrease the aberration of the dark-field detection system and the aberration of the imaging optical system. An interferometer is generally used when measuring the aberration of an optical system in an exposure apparatus. However, this increases the apparatus cost, and increases the apparatus size because an installation space for the interferometer must be secured.
Japanese Patent Laid-Open No. 2007-42965 has disclosed a technique which measures a coma aberration and spherical aberration by using an image of a phase pattern, but this technique has a low measurement accuracy because the sensitivity to the aberration is low. Also, the dark-field detection system uses scattered light or diffracted light, and hence has a light amount smaller than that of a bright-field detection system. This increases the ratio of an error caused by electrical noise of a sensor such as a photoelectric conversion element.